1. Field of the Invention
The present invention relates to an innovative structure for spindle motor, particularly one designed for low cogging and easy downsizing.
2. Description of the Related Art
The advent of the so-called information age is due, in most part, to the proliferation of the mass media and the internet, but the development of the spindle motor, which is most often used in Optical Disk Drives or hard disk drivers to store massive electronic data, also plays a key role.
Nowadays, as compact and lightweight designs have become the mainstream of the market and even the norms of the industry, most electronic products have to be made smaller and smaller to meet consumers' insatiable demand for things slim and small. As a result, the thinning of components in such products is becoming increasingly important. The spindle motor is no exception to this trend. Manufacturers have been making every effort to make it smaller, while at the same time, trying hard to keep, or even increase, its operating performance. As nearly all electronic products are required, either by consideration of user comfort or by a device's need for efficiency and ease of operation, to have stable and smooth running motors, such motors as used in Optical Disk Drives and hard disk drivers all have to meet a very high standard in this respect. As a result, many smooth running micro motors have been developed by industries.
However, development of all these micro motors of the prior art have now reached a bottleneck. Most conventional permanent-magnet motors, for instance, be they brushed or brushless, adopt either a radial air gap or a radial magnetic flux structure. As the motors contain multiple permanent-magnets or a lot of soft magnetic materials, they sometimes produce magnetic cogging that make the motors wobble when the motors are running, generating torque ripples and causing uneven rotation or vibration of the motors.
Another type of motors use the axial air gap or axial magnetic flux structure. They suffer less cogging resulted from magnetic field because they contain little soft magnetic materials, but their flattened, dwarfed structures make them susceptible to axial attractive force, significantly shortening the service life of such parts as the shafts and the bearings. It is obvious that these conventional motors are far from being satisfactory when used in electronic products that require highly smooth and stable running.